secondary battery

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

I want to add a glass mat deep cycle battery in the back of the jeep for the winter , what gauge of wire would be needed ??? I'm not sure how big of a wire I can fish all the way back !!!!!

anybody did something like that ?

Thanks

WWDiesel · **Posted:** Fri Jul 13, 2018 10:37 am

PZKW108 wrote:

I want to add a glass mat deep cycle battery in the back of the jeep for the winter , what gauge of wire would be needed ??? I'm not sure how big of a wire I can fish all the way back !!!!!
anybody did something like that ?
Thanks

Instead of spending a lot of money on a second battery and cables, boxes, etc... you may be better off purchasing a much larger capacity primary battery like an NSB-AGM NorthStar Group 65 which has some impressive specifications to wit:

They are not cheap, but are build in US with virgin lead and will last a very long time.
I have four of them in service now, One in Jeep CRD, one in Dodge 4x4 gaser, and two in a Dodge Cummins diesel with both Dodges having big electric winches.

Any group 65 AGM battery can be used in the Jeep Liberty by slightly modifying the battery tray or better yet purchasing one of Sasquatch's gp. 65 battery trays.
> https://shop.sasquatchparts.com/product ... -2-8l-crd/ <

But if you are intent on adding in a second battery in the back,
Welding cable from your local welding supply store will work very good for the positive cable and it can be bought by the foot.

Another LOST member simply added a second battery under the hood next to the OEM battery. See this thread with pictures:
> viewtopic.php?p=926589#p926589 <

The chart below has been posted before by members on LOST previously but is a very good reference chart for wire size versus distance / AMPS for DC circuits.

rancherman · **Posted:** Fri Jul 13, 2018 11:54 am

I too vote for a singular upgrade, before going with a dual batt; 2 less connections! Less is good sometimes.

But if you want, I'd go at least a 2/0 gauge welding cable. Get the proper tool to crimp the ends on, and heat shrink wrap the connections too.
It gives me the willies running un-fused cable the length of a vehicle though.

WWDiesel · **Posted:** Fri Jul 13, 2018 12:32 pm

rancherman wrote:

It gives me the willies running un-fused cable the length of a vehicle though.

Me Too! Scary thought. :grim:

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

The thing is I'm not looking for cranking !!! I already have a big deep cycle glass mat and it will be perfect for frequent Webasto use in the winter.

For the unfused wiring I guess a guy could put a fuse link in line with the cable !!!

GordnadoCRD · **Posted:** Fri Jul 13, 2018 9:12 pm

Or a breaker at the very least.

k9adv · **Posted:** Wed Jul 25, 2018 7:44 am

yeah, why the presumption it would be unfused?

Billybob · **Posted:** Thu Jul 26, 2018 4:33 am

Yes preferably a breaker....must be a DC Breaker.

Or fit a section of the Fusable Link cable that such as the currently installed section from the alternator to the positive battery terminal....probably expensive though and works only one time! :wink:

GordnadoCRD · **Posted:** Thu Jul 26, 2018 6:19 pm

..and be aware to use a DC circuit breaker that DOES NOT automatically reset. If you do, the circuit may be spared, but you will still end up with a dead battery. Sorry, I failed to mention that before.

TKB4 · **Posted:** Fri Aug 03, 2018 3:42 am

so are you just wanting to keep the deep cycle charged and not actually use it for starting ? BTW its probably overkill but when I put my group 65 in and modified the tray I had a group 31p around from a kubota tractor and I believe it could also fit although might take more modification or even post shortening but specs are impressive and $109 at sams for duracell CA 1170 CCaA 950 and 175 min reserve but since they consider it a commercial battery not much warranty.

WWDiesel · **Posted:** Fri Aug 03, 2018 10:48 am

TKB4 wrote:

so are you just wanting to keep the deep cycle charged and not actually use it for starting ? BTW its probably overkill but when I put my group 65 in and modified the tray I had a group 31p around from a kubota tractor and I believe it could also fit although might take more modification or even post shortening but specs are impressive and $109 at sams for duracell CA 1170 CCaA 950 and 175 min reserve but since they consider it a commercial battery not much warranty.

I have 3 North Star GP 31's in service, one in a Dodge 360 4x4 gasser and two in my Dodge Cummins 4x4. They are impressive batteries to say the least.
I love the fact that they use studs with nuts for cables instead of the problematic posts and clamps, very clean.
But at ~9 1/2 inches high versus ~7 1/2 high for a GP 65 I don't believe you could put one under the hood in at Jeep Liberty in the stock location. :roll:

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

Billybob wrote:

Yes preferably a breaker....must be a DC Breaker.

Or fit a section of the Fusable Link cable that such as the currently installed section from the alternator to the positive battery terminal....probably expensive though and works only one time! :wink:

I'm pretty sure the fuse link can be sourced for dirt cheap in a scrap yard.

The real question is how much current will be drawn from each battery / cables, as the batteries will be hooked in parallel.

I think to calculate the wire size you would have to know how much amp the starter need in the coldest scenario and divide it by 2 ??? maybe I can just go with a wire at least half the size of the starter wire.....

And thank for the chart WW !!

k9adv · **Posted:** Mon Aug 06, 2018 3:25 pm

Dual battery systems are installed all the time with appropriately sized ANL fuses at each end of the positive cable. ANL fuses and fuse blocks are inexpensive.

To presume it wont be fused and cant be done without expensive parts, is inaccurate.

Here is a great resource with some extremely knowledgable input :

https://expeditionportal.com/forum/thre ... -50.77503/

WWDiesel · **Posted:** Mon Aug 06, 2018 9:47 pm

k9adv wrote:

Dual battery systems are installed all the time with appropriately sized ANL fuses at each end of the positive cable. ANL fuses and fuse blocks are inexpensive.
To presume it wont be fused and cant be done without expensive parts, is inaccurate.
Here is a great resource with some extremely knowledgable input :
https://expeditionportal.com/forum/thre ... -50.77503/

Thanks for the link; good to know for future reference.... :wink:

rancherman · **Posted:** Mon Aug 06, 2018 10:22 pm

WWDiesel wrote:

k9adv wrote:

Dual battery systems are installed all the time with appropriately sized ANL fuses at each end of the positive cable. ANL fuses and fuse blocks are inexpensive.
To presume it wont be fused and cant be done without expensive parts, is inaccurate.
Here is a great resource with some extremely knowledgable input :
https://expeditionportal.com/forum/thre ... -50.77503/

Thanks for the link; good to know for future reference.... :wink:

I agree.... now that we know why the need for the second batt..
....most add a 2nd batt in diesels to help with cold crank... Knda blind sided us with the intent.

My question to K9adv is how do you isolate/balance the batteries for charging? No doubt after a 'crank', the 2 batts are going to take different amounts of amps, and possibly at different rates The alternator is just going to bang away at the 'average' of the two, possibly undercharging one, overcharging the other???

GordnadoCRD · **Posted:** Tue Aug 07, 2018 1:22 am

https://www.amazon.com/NOCO-IGD140HP-14 ... 6KFV4?th=1
or appropriate similar.

flash7210 · **Posted:** Tue Aug 07, 2018 9:48 am

Here’s how I would do it.

I would completely isolate the secondary battery from the primary and alternator.

Because the the secondary battery will only be used sparingly, a low current 12v charge controller (5 amp?) could be used to keep the secondary maintained. Something similar to what is used for solar panels.
The charge controller should be powered through a relay by the main battery/alternator on a circuit that is only alive when the key is on. (i.e. not the cigarette lighter)

Use a momentary “boost” switch to activate a solenoid (something similar to an old ford starter solenoid) to join the positive cable of the secondary battery to the positive side of the primary.
The solenoid should be powered by the secondary battery so that if you primary has low voltage, the fully charged secondary can activate the solenoid.

The boost switch should do two things.
1. Activate the solenoid to electrically join the two batteries.
2. Kill power to the charge controller (through the relay) to prevent voltage from back feeding through the charge controller when starting the engine.

This is how it should work:
1. Turn key on
2. Hold ON the boost switch, joining the two batteries and killing the charge controller.
3. Start engine with both batteries
4. Release boost switch, killing the solenoid and activating the charge controller

I have a truck at work that used this kind of setup where the secondary batteries are used to power an inverter. Works pretty good as long as you don’t forget to turn off the inverter.

k9adv · **Posted:** Tue Aug 07, 2018 10:12 am

i use this, a Samlex 160 ACR, it is a dual voltage sensing relay, and then do a Victron 75 mppt solar charge controller to auxiliary.

I have a 3 way switch in dash that allows the ACR to do it's thing, or i can force separate the batteries, or force connect (so i can jump start myself from the front seat).

Works perfectly, has for years.

http://www.samlexamerica.com/products/P ... px?pid=482

rancherman · **Posted:** Tue Aug 07, 2018 1:55 pm

k9adv wrote:

i use this, a Samlex 160 ACR, it is a dual voltage sensing relay, and then do a Victron 75 mppt solar charge controller to auxiliary.

I have a 3 way switch in dash that allows the ACR to do it's thing, or i can force separate the batteries, or force connect (so i can jump start myself from the front seat).

Works perfectly, has for years.

http://www.samlexamerica.com/products/P ... px?pid=482

Cool! I have some 'non jeep' projects that could utilize this! Thanks

secondary battery

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